PEA2PbI4: fast two-dimensional lead iodide perovskite scintillator with green and red emission

Among the two-dimensional hybrid organic-inorganic perovskites, PEA2PbBr4 is one of the best scintillators combining high light yield and fast nanosecond decay time. However, it has limited sensitivity to X-ray and positron emission tomography because of insufficient mass density and effective atomic number. In this article, we show that exchanging the halide from bromide to iodide allows to shorten the absorption length as much as two times for X-ray energies. We present a detailed study on scintillation properties of self-grown samples of PEA2PbI4 crystal, which we compare with the previously reported results for PEA2PbBr4 crystal. The synthesis method of PEA2PbI4 crystal is based on dissolving the perovskite precursors in hydroiodic acid, which is then stirred and left for evaporation. Our measurements include the characterizations with optical, X-ray, and γ-ray sources. We observe two emission bands of PEA2PbI4 crystal centered at 532 (green) and 660 (red) nm, and we link them to the scintillation mechanisms involving exciton and surface defect states. We also report the scintillation light yields of 1,000 and 10,000 photons/MeV at room temperature and 10 K, respectively, and the coincidence timing resolution full width at half maximum of 138 ps, and the fast component in scintillation decay curve of 0.5 ns. This fast component is much faster than that of 13.4 ns of PEA2PbBr4 crystal, and with two times shorter absorption length, it secures better opportunities in timing applications in particular time-of-flight positron emission tomography and high energy physics.